Processing and Geometric Effects on Mechanical Properties of Printed Multimaterial Glass-Reinforced Photopolymers

Multimaterial additive manufacturing offers the potential to create functionally graded components from highly filled photocurable particle-reinforced composites (PRCs). While prior research has focused on 3D printing photocurable slurries with high volume loadings, the mechanical properties of multimaterial interfaces have not been measured. Furthermore, the effects of spatially varying photocuring on highly filled PRCs have not been quantified. To address these issues, this study isolated the effects of 3D-printed multi-extrusion and multimaterial coplanar interfaces on the ultimate tensile strengths (UTSs) for two glass-reinforced photocurable formulations under different processing conditions. Tensile specimens were manufactured via casting and vibration-assisted printing, and their UTSs and bulk porosities were measured. Multiple materials at the interface had a negligible effect on the rupture location compared to discontinuities in the print toolpath. Furthermore, the contributors to UTSs in descending order of importance were altered slurry composition and decreased porosity from vacuum processing, stress concentrations from tensile specimen geometry, and nonuniform photocuring. Understanding the effects of the material and processing conditions on the interface is important when designing high-performance, functionally graded PRCs for aerospace applications, for which this study lays the groundwork.